JP7303808B2 - Method for producing polyvinyl alcohol - Google Patents
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F18/00—Homopolymers and copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an acyloxy radical of a saturated carboxylic acid, of carbonic acid or of a haloformic acid
- C08F18/02—Esters of monocarboxylic acids
- C08F18/04—Vinyl esters
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F8/00—Chemical modification by after-treatment
- C08F8/12—Hydrolysis
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F18/00—Homopolymers and copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an acyloxy radical of a saturated carboxylic acid, of carbonic acid or of a haloformic acid
- C08F18/02—Esters of monocarboxylic acids
- C08F18/04—Vinyl esters
- C08F18/08—Vinyl acetate
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- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F216/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal or ketal radical
- C08F216/02—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal or ketal radical by an alcohol radical
- C08F216/04—Acyclic compounds
- C08F216/06—Polyvinyl alcohol ; Vinyl alcohol
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L31/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an acyloxy radical of a saturated carboxylic acid, of carbonic acid or of a haloformic acid; Compositions of derivatives of such polymers
- C08L31/02—Homopolymers or copolymers of esters of monocarboxylic acids
- C08L31/04—Homopolymers or copolymers of vinyl acetate
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Description
本発明は、高重合度ポリビニルアルコールの製造方法に関する。 TECHNICAL FIELD The present invention relates to a method for producing polyvinyl alcohol with a high degree of polymerization.
ポリビニルアルコールは、ビニロン繊維、水溶性フィルム、偏光膜用原料フィルム、紙用サイジング剤、繊維用サイジング剤、接着剤、懸濁重合用分散剤、乳化重合用分散剤などの原料として広く使用されている。 Polyvinyl alcohol is widely used as a raw material for vinylon fibers, water-soluble films, raw films for polarizing films, paper sizing agents, fiber sizing agents, adhesives, suspension polymerization dispersants, emulsion polymerization dispersants, etc. there is
高重合度ポリビニルアルコールの製造方法としては、20℃以下の低温下で重合速度を10%/時間以下として懸濁重合する方法(特許文献1)、特定の乳化剤を用い15℃以下で乳化重合する方法(特許文献2)、10℃以下で光乳化重合する方法(特許文献3)などが知られている。 As a method for producing polyvinyl alcohol with a high degree of polymerization, a method of suspension polymerization at a low temperature of 20 ° C. or less at a polymerization rate of 10% / hour or less (Patent Document 1), and an emulsion polymerization of 15 ° C. or less using a specific emulsifier. A method (Patent Document 2), a method of photoemulsion polymerization at 10° C. or less (Patent Document 3), and the like are known.
しかしながら、これらの方法は、著しく生産性に劣る、得られたポリビニルアルコールの機械的強度が充分ではないなどの問題点を有していた。 However, these methods have problems such as markedly inferior productivity and insufficient mechanical strength of the resulting polyvinyl alcohol.
本発明は、機械的強度に優れるポリビニルアルコールを、生産性を著しく損なうことなく製造する方法を提供するものである。 The present invention provides a method for producing polyvinyl alcohol having excellent mechanical strength without significantly impairing productivity.
このような目的は、下記[1]~[11]に例示する本発明により達成される。
[1]
ビニルエステル系単量体を重合温度10℃以上50℃以下で、重合率10%以上70%以下として懸濁重合してビニルエステル系重合体を得る工程と、
ビニルエステル系重合体をアルコール系溶媒に溶解する工程と、
溶解されたビニルエステル系重合体のアルコール系溶液にケン化触媒を加えてケン化反応を行う工程と、
を含む、平均重合度が5.0×103以上1.5×104以下であるポリビニルアルコールの製造方法。
[2]
前記懸濁重合の重合温度(T)とビニルエステル系単量体の重合率(X)を以下の式(1)を満たすように設定する[1]に記載のポリビニルアルコールの製造方法。
X ≦ -0.05T2+1.5T+60 式(1)
(式(1)において、Tは重合温度(℃)を表し、Xは重合率(質量%)(0<X<100)を表す。)
[3]
前記ビニルエステル系重合体をアルコール系溶媒に溶解する工程に供するビニルエステル系重合体のメジアン径が100~800μmである[1]または[2]に記載のポリビニルアルコールの製造方法。
[4]
前記懸濁重合の際、下記化学式Iで示される構造を有する変性ポリビニルアルコールを添加する工程を有する[1]乃至[3]の何れか一項に記載のポリビニルアルコールの製造方法。
[5]
アルコール系溶媒に溶解する工程に供する前記ビニルエステル系重合体は、レーザー回折・散乱式粒度分布測定法により測定される体積基準の粒度分布から、
メジアン径(d50)を基準としたときの標準偏差(σ50)を測定し、CV値(σ50/d50×100)を算出すると、
CV値が0.4~0.9である[1]乃至[4]の何れか一項に記載のポリビニルアルコールの製造方法。
[6]
前記懸濁重合の際に重合停止剤を加えてビニルエステル系単量体の重合を停止する工程を含む[1]乃至[5]の何れか一項に記載のポリビニルアルコールの製造方法。
[7]
前記重合停止剤は、下記化学式IIで示される構造を有する化合物を含む[6]に記載のポリビニルアルコールの製造方法。
[8]
前記重合停止剤は、下記化学式IIIで示される共役ジエン構造を有する不飽和カルボン酸系化合物を含む[6]に記載のポリビニルアルコールの製造方法。
[9]
前記重合停止剤は、ニトロソ化合物を含む[6]に記載のポリビニルアルコールの製造方法。
[10]
重合停止剤として、酸素含有ガスを使用する[6]乃至[9]のいずれか一項に記載のポリビニルアルコールの製造方法。
[11]
前記ビニルエステル系重合体をアルコール系溶媒に溶解する工程において、不揮発分が30~90質量%となるよう調整する工程を有する[1]乃至[10]のいずれか一項に記載のポリビニルアルコールの製造方法。Such objects are achieved by the present invention exemplified in [1] to [11] below.
[1]
a step of suspension polymerizing a vinyl ester monomer at a polymerization temperature of 10° C. or higher and 50° C. or lower at a polymerization rate of 10% or higher and 70% or lower to obtain a vinyl ester polymer;
a step of dissolving a vinyl ester-based polymer in an alcohol-based solvent;
a step of adding a saponification catalyst to the alcohol-based solution of the dissolved vinyl ester-based polymer to perform a saponification reaction;
A method for producing polyvinyl alcohol having an average degree of polymerization of 5.0×10 3 or more and 1.5×10 4 or less.
[2]
The method for producing polyvinyl alcohol according to [1], wherein the polymerization temperature (T) of the suspension polymerization and the polymerization rate (X) of the vinyl ester monomer are set so as to satisfy the following formula (1).
X≦−0.05T 2 +1.5T+60 Formula (1)
(In formula (1), T represents the polymerization temperature (° C.), and X represents the rate of polymerization (% by mass) (0<X<100).)
[3]
The method for producing polyvinyl alcohol according to [1] or [2], wherein the vinyl ester polymer subjected to the step of dissolving the vinyl ester polymer in the alcohol solvent has a median diameter of 100 to 800 μm.
[4]
The method for producing polyvinyl alcohol according to any one of [1] to [3], which comprises adding modified polyvinyl alcohol having a structure represented by the following chemical formula I during the suspension polymerization.
[5]
The vinyl ester polymer subjected to the step of dissolving in an alcohol solvent has a volume-based particle size distribution measured by a laser diffraction/scattering particle size distribution measurement method,
When the standard deviation (σ50) is measured with respect to the median diameter (d50) and the CV value (σ50/d50×100) is calculated,
The method for producing polyvinyl alcohol according to any one of [1] to [4], which has a CV value of 0.4 to 0.9.
[6]
The method for producing polyvinyl alcohol according to any one of [1] to [5], including a step of adding a polymerization terminator to terminate the polymerization of the vinyl ester monomer during the suspension polymerization.
[7]
The method for producing polyvinyl alcohol according to [6], wherein the polymerization terminator contains a compound having a structure represented by the following chemical formula II.
[8]
The method for producing polyvinyl alcohol according to [6], wherein the polymerization terminator contains an unsaturated carboxylic acid compound having a conjugated diene structure represented by the following chemical formula III.
[9]
The method for producing polyvinyl alcohol according to [6], wherein the polymerization terminator contains a nitroso compound.
[10]
The method for producing polyvinyl alcohol according to any one of [6] to [9], wherein an oxygen-containing gas is used as the polymerization terminator.
[11]
The polyvinyl alcohol according to any one of [1] to [10], which has a step of adjusting the nonvolatile content to 30 to 90% by mass in the step of dissolving the vinyl ester polymer in an alcohol solvent. Production method.
本発明によれば、機械的強度に優れるポリビニルアルコールを、生産性を著しく損なうことなく製造することができる。 According to the present invention, polyvinyl alcohol having excellent mechanical strength can be produced without significantly impairing productivity.
本発明に係るポリビニルアルコールの製造方法の一実施形態においては、(A)ビニルエステル系単量体を重合温度10~50℃、重合率10~70%で懸濁重合してビニルエステル系重合体を製造する工程(懸濁重合工程)
(B)得られたビニルエステル系重合体をアルコール系溶媒に溶解する工程
(C)前工程で溶解されたビニルエステル系重合体のアルコール系溶液にケン化触媒を加えてケン化反応を行い、ポリビニルアルコールとする工程
を含む製造方法により、平均重合度が5.0×103以上1.5×104以下であるポリビニルアルコールを製造する。当該製造方法によれば、機械的強度に優れる高重合度のポリビニルアルコールを、生産性を著しく損なうことなく製造できる。In one embodiment of the method for producing polyvinyl alcohol according to the present invention, (A) a vinyl ester monomer is subjected to suspension polymerization at a polymerization temperature of 10 to 50° C. and a polymerization rate of 10 to 70% to obtain a vinyl ester polymer. Manufacturing process (suspension polymerization process)
(B) a step of dissolving the obtained vinyl ester polymer in an alcoholic solvent; Polyvinyl alcohol having an average degree of polymerization of 5.0×10 3 or more and 1.5×10 4 or less is produced by a production method including a step of forming polyvinyl alcohol. According to the production method, polyvinyl alcohol having a high degree of polymerization and excellent mechanical strength can be produced without significantly impairing productivity.
<重合度>
本発明で製造するポリビニルアルコールの平均重合度は5.0×103以上1.5×104以下であることが好ましい。重合温度や重合率の制御範囲を変更することで該範囲を外れるポリビニルアルコールを製造することも可能ではあるが、平均重合度が5.0×103を下回る場合、本発明の方法で得られる様な機械的強度に優れるポリビニルアルコールとはならない欠点がある。また、平均重合度が1.5×104を超えても機械的強度の向上効果は限定的であり、寧ろ生産性が著しく低下する欠点の方が大きくなる。
平均重合度の制御は、重合温度、重合率、重合速度(重合率の単位時間当たりの変化速度)を調整することで可能である。また、少量の連鎖移動剤の存在下で重合を行う方法によっても平均重合度の制御は可能である。<Degree of polymerization>
The average degree of polymerization of polyvinyl alcohol produced in the present invention is preferably 5.0×10 3 or more and 1.5×10 4 or less. Although it is possible to produce polyvinyl alcohol outside these ranges by changing the control ranges of the polymerization temperature and polymerization rate, if the average degree of polymerization is less than 5.0×10 3 , the method of the present invention can produce However, it has a drawback that it cannot be a polyvinyl alcohol having excellent mechanical strength. Further, even if the average degree of polymerization exceeds 1.5×10 4 , the effect of improving the mechanical strength is limited, and rather the disadvantage of a marked decrease in productivity becomes larger.
The average degree of polymerization can be controlled by adjusting the polymerization temperature, polymerization rate, and polymerization rate (change rate of polymerization rate per unit time). The average degree of polymerization can also be controlled by a method of conducting polymerization in the presence of a small amount of chain transfer agent.
尚、本発明で云う重合度は、JIS K6726:1994に準拠する方法にて、測定される平均重合度を意味する。すなわち、ビニルエステル系重合体を完全にケン化し、精製した後、30℃の水中で測定して得られた相対粘度から算出した極限粘度[η]から求める。 In addition, the polymerization degree said by this invention means the average polymerization degree measured by the method based on JISK6726:1994. That is, the intrinsic viscosity [η] calculated from the relative viscosity obtained by measuring the vinyl ester polymer in water at 30° C. after completely saponifying and purifying the vinyl ester polymer is obtained.
<重合率>
ビニルエステル系単量体の懸濁重合は、重合率10質量%以上70質量%以下の範囲で止めることが必須である。重合率が10質量%未満の場合だと、生産効率が低いという欠点がある。また、重合率が70質量%超の場合だと、得られたビニルエステル系重合体のアルコール系溶媒への溶解性が低下して生産性が低下する、更には得られるポリビニルアルコールの機械的強度が低下するといった問題がある。重合率の下限値は好ましくは20質量%以上であり、より好ましくは30質量%以上である。重合率の上限値は好ましくは60質量%以下である。この際、(A)懸濁重合工程における重合温度(T)とビニルエステル系単量体の重合率(X)の関係を次式(1)を満たすように設定することで、本発明の効果を更に高めることが可能となる。得られたポリビニルアルコールの機械的強度と生産性のバランスを考慮すると、重合温度は20~40℃の間とすることがより好ましく、25~35℃の間が更に好ましい。
X ≦ -0.05T2+1.5T+60 式(1)
(式1において、Tは重合温度(℃)を表し、Xは重合率(質量%)(0<X<100)を表す。)
式(1)を外れた場合、ビニルエステル系重合体のアルコール系溶媒に対する溶解性が低下する。ここでいう溶解性の低下は、ビニルエステル系重合体のアルコール系溶媒に対する溶解時間が長くなることや、アルコール系溶媒への溶解時にビニルエステル系重合体の未溶解量の増加を指す。さらに式(1)を外れた場合、重合終了後の重合缶への未溶解の付着物が多くなるという生産性の低下を招く。
尚、ここで云う重合率とは、重合に用いたビニルエステル系単量体のうち、重合体へと反応した割合のことであり、質量%で表される。本発明において重合率はポリマー濃度測定法で測定される値を指す。つまり、重合中に重合液をサンプリングしてその重量を測り、モノマー及び溶媒を留去して得られるポリマーの重量を元に重合液のポリマー濃度を算出して、モノマーに対するポリマー量を求めて重合率を算出する。<Polymerization rate>
Suspension polymerization of vinyl ester monomers must be stopped at a polymerization rate of 10% by mass or more and 70% by mass or less. If the polymerization rate is less than 10% by mass, there is a drawback that the production efficiency is low. Further, when the polymerization rate exceeds 70% by mass, the solubility of the resulting vinyl ester polymer in an alcohol solvent decreases, resulting in a decrease in productivity, and the mechanical strength of the resulting polyvinyl alcohol. There is a problem that the The lower limit of the polymerization rate is preferably 20% by mass or more, more preferably 30% by mass or more. The upper limit of the polymerization rate is preferably 60% by mass or less. At this time, the effect of the present invention is obtained by setting the relationship between the polymerization temperature (T) and the polymerization rate (X) of the vinyl ester monomer in the (A) suspension polymerization step so as to satisfy the following formula (1). can be further increased. Considering the balance between the mechanical strength and productivity of the resulting polyvinyl alcohol, the polymerization temperature is more preferably between 20 and 40.degree. C., still more preferably between 25 and 35.degree.
X≦−0.05T 2 +1.5T+60 Formula (1)
(In Formula 1, T represents the polymerization temperature (° C.), and X represents the rate of polymerization (% by mass) (0<X<100).)
If the formula (1) is not satisfied, the solubility of the vinyl ester polymer in an alcohol solvent is reduced. The term "decrease in solubility" as used herein refers to a longer dissolution time of the vinyl ester polymer in the alcohol solvent or an increase in the undissolved amount of the vinyl ester polymer when dissolved in the alcohol solvent. Furthermore, if the formula (1) is not satisfied, the productivity will be lowered because undissolved deposits on the polymerization vessel after the completion of the polymerization will increase.
The polymerization rate referred to herein is the proportion of the vinyl ester monomers used in the polymerization that have reacted to form a polymer, and is expressed in mass %. In the present invention, the polymerization rate refers to a value measured by a polymer concentration measurement method. In other words, the polymer concentration of the polymerization solution is calculated based on the weight of the polymer obtained by distilling off the monomers and solvent, and the amount of polymer relative to the monomer is determined and polymerized. Calculate the rate.
<単量体>
本発明に用いられるビニルエステル系単量体は、単独使用でも複数種類の混合使用でも良いが、作業の簡便さなどから単独使用の方が推奨される。ビニルエステル系単量体としては、例えばギ酸ビニル、酢酸ビニル、プロピオン酸ビニル、バレリン酸ビニル、カプリン酸ビニル、ラウリン酸ビニル、ステアリン酸ビニル、安息香酸ビニル、ピバリン酸ビニル等が例示される。重合のし易さ、入手のし易さ等の観点から、酢酸ビニルの使用が好ましい。<monomer>
The vinyl ester-based monomers used in the present invention may be used singly or in a mixture of a plurality of types, but single use is recommended from the standpoint of ease of work and the like. Examples of vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, and vinyl pivalate. The use of vinyl acetate is preferred from the viewpoints of ease of polymerization, availability, and the like.
本発明では、本発明の効果を損なわない範囲でビニルエステル系単量体と共重合可能なビニルエステル系単量体以外の単量体を併用することも可能である。そのような単量体としては、例えば、エチレン、プロピレン等のα-オレフィン単量体、(メタ)アクリル酸メチル、(メタ)アクリル酸エチル、(メタ)アクリル酸ブチル、(メタ)アクリル酸2-エチルヘキシル等の(メタ)アクリル酸アルキルエステル単量体、(メタ)アクリルアミド、N-メチロールアクリルアミド等の不飽和アミド単量体、(メタ)アクリル酸、クロトン酸、マレイン酸、イタコン酸、フマル酸等の不飽和カルボン酸単量体、不飽和カルボン酸のアルキル(メチル、エチル、プロピル等)エステル単量体、無水マレイン酸等の不飽和カルボン酸の無水物、不飽和カルボン酸のナトリウム、カリウム、アンモニウム等との塩、アリルグリシジルエーテル、グリシジル(メタ) アクリレート等のグリシジル基含有単量体、2-アクリルアミド-2-メチルプロパンスルホン酸等のスルホン酸基含有単量体又はその塩、アシッドホスホオキシエチルメタアクリレート、アシッドホスホオキシプロピルメタアクリレート等のリン酸基含有単量体、アルキルビニルエーテル単量体などが挙げられる。これらビニルエステル系単量体以外の単量体の使用量は、本発明の効果を充分に発揮させる観点からは、ビニルエステル系単量体に対し、5モル%以下が好ましく、より好ましくは2モル%以下、更に好ましくは1モル%以下である。 In the present invention, a monomer other than the vinyl ester-based monomer copolymerizable with the vinyl ester-based monomer may be used in combination within a range that does not impair the effects of the present invention. Examples of such monomers include α-olefin monomers such as ethylene and propylene, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, (meth)acrylic acid 2 -(meth)acrylic acid alkyl ester monomers such as ethylhexyl, (meth)acrylamide, unsaturated amide monomers such as N-methylolacrylamide, (meth)acrylic acid, crotonic acid, maleic acid, itaconic acid, fumaric acid etc., unsaturated carboxylic acid alkyl (methyl, ethyl, propyl, etc.) ester monomers, unsaturated carboxylic acid anhydrides such as maleic anhydride, unsaturated carboxylic acid sodium, potassium , salts with ammonium, etc., allyl glycidyl ether, glycidyl group-containing monomers such as glycidyl (meth) acrylate, sulfonic acid group-containing monomers such as 2-acrylamido-2-methylpropanesulfonic acid or salts thereof, acid phosphor phosphate group-containing monomers such as oxyethyl methacrylate and acid phosphooxypropyl methacrylate; and alkyl vinyl ether monomers. From the viewpoint of sufficiently exhibiting the effects of the present invention, the amount of monomers other than these vinyl ester-based monomers used is preferably 5 mol % or less, more preferably 2 mol %, based on the vinyl ester-based monomers. It is mol % or less, more preferably 1 mol % or less.
<重合開始剤>
ビニルエステル系単量体を懸濁重合する際の重合開始剤は、特に限定するものではないが、アゾビスイソブチロニトリル、アゾビス-2,4-ジメチルバレロニトリル、アゾビス(4-メトキシ-2,4-ジメチルバレロニトリル)、アゾビスジメチルバレロニトリル、アゾビスメトキシバレロニトリルなどのアゾ化合物、アセチルパーオキサイド、ベンゾイルパーオキサイド、ラウロイルパーオキサイド、アセチルシクロヘキシルスルホニルパーオキサイド、2,4,4-トリメチルペンチル-2-パーオキシフェノキシアセテートなどの過酸化物、ジイソプピルパーオキシジカーボネート、ジ-2-エチルヘキシルパーオキシジカーボネート、ジエトキシエチルパーオキシジカーボネートなどのパーカーボネート化合物、t-ブチルパーオキシネオデカネート、α-クミルパーオキシネオデカネートなどのパーエステル化合物などを単独又は組み合わせて使用することができる。本発明では低温で重合することから、アゾビス(4-メトキシ-2,4-ジメチルバレロニトリル)の使用が好ましい。<Polymerization initiator>
Polymerization initiators for suspension polymerization of vinyl ester monomers are not particularly limited, but azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, azobis(4-methoxy-2 ,4-dimethylvaleronitrile), azo compounds such as azobisdimethylvaleronitrile, azobismethoxyvaleronitrile, acetyl peroxide, benzoyl peroxide, lauroyl peroxide, acetylcyclohexylsulfonyl peroxide, 2,4,4-trimethylpentyl -Peroxides such as 2-peroxyphenoxyacetate, peroxycarbonate compounds such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, diethoxyethyl peroxydicarbonate, t-butyl peroxyneo Perester compounds such as decanoate and α-cumyl peroxyneodecanate can be used alone or in combination. In the present invention, the use of azobis(4-methoxy-2,4-dimethylvaleronitrile) is preferred because it polymerizes at low temperatures.
<ビニルエステル系重合体の粒径分布>
懸濁重合で得られるビニルエステル系重合体粒子は、メジアン径が100~800μmに調整されることが好ましい。メジアン径はより好ましくは150~500μm、更に好ましくは200~400μmである。メジアン径を該範囲に調整することで、重合中の懸濁粒子の安定性と、次の工程でビニルエステル系重合体をアルコール系溶媒に溶解する際の溶解作業の軽減化が可能となる。
ビニルエステル系重合体粒子のメジアン径は、反応缶の撹拌動力及び使用する分散剤の種類や量を調整することで制御可能である。一般的に撹拌動力が上がるほど、また分散剤添加量が増えるほど、メジアン径は小さくなる。メジアン径はビニルエステル系重合体粒子に対して篩別等の粒径選別工程を実施することで制御することも可能である。
本発明において、ビニルエステル系重合体粒子のメジアン径(d50)は、レーザー回折・散乱式粒度分布測定法により体積基準の累積粒度分布を測定することで求められる。<Particle size distribution of vinyl ester polymer>
The vinyl ester polymer particles obtained by suspension polymerization are preferably adjusted to have a median diameter of 100 to 800 μm. The median diameter is more preferably 150-500 μm, still more preferably 200-400 μm. By adjusting the median diameter within this range, it becomes possible to stabilize the suspended particles during polymerization and to reduce the dissolution work when dissolving the vinyl ester polymer in the alcohol solvent in the next step.
The median diameter of the vinyl ester polymer particles can be controlled by adjusting the stirring power of the reactor and the type and amount of the dispersant used. In general, the higher the stirring power and the higher the amount of dispersant added, the smaller the median diameter. The median diameter can also be controlled by subjecting the vinyl ester polymer particles to a particle size selection process such as sieving.
In the present invention, the median diameter (d50) of the vinyl ester polymer particles is obtained by measuring the volume-based cumulative particle size distribution by a laser diffraction/scattering particle size distribution measuring method.
また、ビニルエステル系重合体粒子について、レーザー回折・散乱式粒度分布測定法により測定される体積基準の粒度分布から、メジアン径(d50)を基準としたときの標準偏差(σ50)を測定し、CV値(σ50/d50×100)を算出すると、CV値が2.0以下であることが好ましい。CV値が2.0以下であるということは粒度分布が狭いことを示す。細かい粒子の含有量が多いと、脱モノマーの効率が低下し問題であり、また粗い粒子の含有量が多いと、アルコール系溶媒への溶解性に影響し、問題となる。CV値は好ましくは1.5以下であり、より好ましくは1.0以下であり、更により好ましくは0.4~0.9であり、例えば0.2~2.0とすることができる。 Further, for the vinyl ester polymer particles, the standard deviation (σ50) is measured based on the median diameter (d50) from the volume-based particle size distribution measured by the laser diffraction/scattering particle size distribution measurement method, When the CV value (σ50/d50×100) is calculated, the CV value is preferably 2.0 or less. A CV value of 2.0 or less indicates a narrow particle size distribution. If the content of fine particles is large, the efficiency of demonomering is lowered, and if the content of coarse particles is large, solubility in alcoholic solvents is affected and becomes a problem. The CV value is preferably 1.5 or less, more preferably 1.0 or less, still more preferably 0.4 to 0.9, for example 0.2 to 2.0.
<分散剤>
懸濁重合の際に使用する分散剤に特段の制約は無く、一般的に使用されるポリビニルアルコール系分散剤、セルロース系分散剤、ポリビニルピロリドン、アクリル酸またはその塩、メタクリル酸またはその塩、ポリ(メタ)アクリルアミド類等が使用可能である。懸濁重合の際の分散安定性や最終的にポリビニルアルコールとすることなどを鑑みた場合、ポリビニルアルコール系分散剤の使用が好ましく、中でも下記化学式Iで示される構造単位を有する変性ポリビニルアルコールを使用することが好ましい。この変性ポリビニルアルコールを使用することで、少量の添加(1000ppm/モノマー)で分散安定性を維持することが可能となる。この変性ポリビニルアルコールは公知であり、例えば、特開2010-202840号、特開2014-31487号及び特開2015-187215号に記載されている。
炭素数1~12のアルキル基の中では、炭素数が少ない方が粘度が低く取り扱いやすいことや、原料が安価なこと等の理由により、炭素数1~2の低級アルコールが好ましい。金属原子としては、アルカリ金属またはアルカリ土類金属が好ましい。<Dispersant>
There are no particular restrictions on the dispersant used during suspension polymerization, and commonly used polyvinyl alcohol-based dispersants, cellulose-based dispersants, polyvinylpyrrolidone, acrylic acid or its salts, methacrylic acid or its salts, poly (Meth)acrylamides and the like can be used. Considering the dispersion stability during suspension polymerization and the final use of polyvinyl alcohol, it is preferable to use a polyvinyl alcohol-based dispersant. preferably. By using this modified polyvinyl alcohol, it becomes possible to maintain the dispersion stability with a small amount of addition (1000 ppm/monomer). This modified polyvinyl alcohol is known and described, for example, in JP-A-2010-202840, JP-A-2014-31487 and JP-A-2015-187215.
Among the alkyl groups having 1 to 12 carbon atoms, lower alcohols having 1 to 2 carbon atoms are preferable because the viscosity is lower when the number of carbon atoms is less and the raw material is inexpensive. As metal atoms, alkali metals or alkaline earth metals are preferred.
<重合停止剤>
先述したように、ビニルエステル系単量体の懸濁重合は、重合率10~70%で止めることが必須である。重合の停止は、反応液を反応温度よりも更に低温にすることでも可能ではあるが、重合率を確実に制御するためには、重合停止剤によって重合を停止させることが好ましい。この際の重合停止剤としては、特に制限されるものではないが、下記化学式IIで示されるカテコール構造を有する化合物、下記化学式IIIで示される共役ジエン構造を有する化合物、ニトロソ構造を有する化合物、酸素含有ガス(例:空気、酸素)を使用することが好ましい。これらは単独で使用してもよく、二種以上を組み合わせて使用してもよい。空気または酸素を使用する場合は、保安上の理由により窒素等の不活性ガスで希釈してからの使用がより好ましい。<Polymerization terminator>
As described above, the suspension polymerization of vinyl ester monomers must be stopped at a polymerization rate of 10 to 70%. Although the polymerization can be terminated by lowering the temperature of the reaction solution below the reaction temperature, it is preferable to terminate the polymerization with a polymerization terminator in order to reliably control the polymerization rate. The polymerization terminator at this time is not particularly limited, but a compound having a catechol structure represented by the following chemical formula II, a compound having a conjugated diene structure represented by the following chemical formula III, a compound having a nitroso structure, oxygen Containing gases (eg air, oxygen) are preferably used. These may be used alone or in combination of two or more. When air or oxygen is used, it is more preferable to use it after diluting it with an inert gas such as nitrogen for safety reasons.
炭素数1~8の低級アルキル基の中では、tert-ブチル基、イソブチル基やイソプロピル基などかさ高い方が重合停止効果の観点から好ましいので、炭素数3以上が好ましい。
化学式IIで示されるカテコール構造を有する化合物としては、具体的には4-tert-ブチルカテコール等が例示される。
Among the lower alkyl groups having 1 to 8 carbon atoms, bulky groups such as tert-butyl, isobutyl and isopropyl groups are preferred from the viewpoint of the effect of terminating polymerization, and therefore those having 3 or more carbon atoms are preferred.
Specific examples of compounds having a catechol structure represented by Chemical Formula II include 4-tert-butyl catechol.
炭素数1~4の低級アルキル基の中では、重合停止効果が高く、また原料が安価なことから炭素数1が好ましい。アルキルフェニル基の中では、炭素数が少ない方が粘度が低く取り扱いやすいため、炭素数1~4の低級アルキル基をもつアルキルフェニル基が好ましい。化学式IIIで示される共役ジエン構造を有する不飽和カルボン酸系化合物としては、具体的にはソルビン酸等が例示される。
Among the lower alkyl groups having 1 to 4 carbon atoms, 1 carbon atom is preferable because the effect of terminating polymerization is high and raw materials are inexpensive. Among alkylphenyl groups, alkylphenyl groups having a lower alkyl group having 1 to 4 carbon atoms are preferred, since those with fewer carbon atoms have lower viscosity and are easier to handle. Specific examples of unsaturated carboxylic acid compounds having a conjugated diene structure represented by Chemical Formula III include sorbic acid and the like.
ニトロソ構造を有する化合物としては、具体的にはクペロン等が例示される。 A specific example of the compound having a nitroso structure is cupferron.
これら重合停止剤を使用することで、重合を確実に停止できるとともに、得られたポリビニルアルコールの着色を防止することが可能となる。重合停止剤の添加量は重合開始剤の1倍モル以上、3倍モル以下が好ましい。1倍モル未満の場合、重合が停止しない場合があり、また3倍モル超の場合不純物として系内に残存する。また重合缶内に残存してしまい次工程の重合反応への影響がある。 By using these polymerization terminators, it is possible to reliably terminate the polymerization and prevent the resulting polyvinyl alcohol from being colored. The amount of the polymerization terminator to be added is preferably 1 to 3 times the molar amount of the polymerization initiator. If it is less than 1-fold mol, the polymerization may not be terminated, and if it exceeds 3-fold mol, it will remain in the system as an impurity. Moreover, it may remain in the polymerization vessel and affect the polymerization reaction in the next step.
<脱モノマー>
重合を停止後、未反応のビニルエステル系単量体を除去するために脱モノマーを行う。脱モノマーの方法は、特に制限されるものではなく、何れの方法を採用しても良いが、反応液を減圧下で加熱しながら未反応の単量体を系外へ留出させる方法が簡便であり推奨される。
未反応モノマーを除去した反応液中から、濾過、乾燥することでビニルエステル系重合体が得られる。乾燥工程を省略して次の溶解工程へ供することも可能ではあるが、水分含有量のバラツキによりケン化反応の制御が難しくなることから、乾燥した後に溶解工程へ供することが推奨される。<Demonomerization>
After stopping the polymerization, demonomerization is performed to remove unreacted vinyl ester monomers. The method of demonomerization is not particularly limited, and any method may be employed. and recommended.
A vinyl ester polymer is obtained by filtering and drying the reaction solution from which unreacted monomers have been removed. Although it is possible to omit the drying step and apply to the next dissolving step, it is recommended to apply to the dissolving step after drying because it becomes difficult to control the saponification reaction due to variations in water content.
<ケン化>
懸濁重合で得られたビニルエステル系重合体は、アルコール系溶媒に溶解される。この際に使用するアルコール系溶媒としては、メタノール、エタノール、ブタノール等が挙げられるが、メタノールの使用が好ましい。アルコール系溶媒中の重合体(不揮発分)の濃度は、30~90質量%の範囲が好ましく、より好ましくは40~88質量%、更に好ましくは50~85質量%である。不揮発分濃度を当該範囲とすることで、ケン化によって得られるポリビニルアルコールの粒子が微細化するという利点が得られる。不揮発分量は、ビニルエステル系重合体のアルコール溶液を150℃で30分間乾燥させ、残った固形分の重量から算出する。<Saponification>
A vinyl ester polymer obtained by suspension polymerization is dissolved in an alcohol solvent. Examples of the alcoholic solvent used in this case include methanol, ethanol, butanol and the like, and the use of methanol is preferred. The concentration of the polymer (non-volatile matter) in the alcoholic solvent is preferably in the range of 30-90% by mass, more preferably 40-88% by mass, still more preferably 50-85% by mass. By setting the non-volatile content concentration within the above range, there is an advantage that the polyvinyl alcohol particles obtained by saponification are made finer. The non-volatile content is calculated from the weight of the remaining solid content after drying the alcohol solution of the vinyl ester polymer at 150° C. for 30 minutes.
溶解装置については、特に制限されるものではなく、各種の溶解缶が使用可能であるが、重合体の濃度を高めたい場合にはニーダー型混練機を溶解缶として使用することが推奨される。ニーダー型混練機を使用することで、溶液粘度が高粘度となった際にも撹拌が可能であり、かつ溶解に掛かる時間も短縮することが可能となる。 The dissolving apparatus is not particularly limited, and various dissolving cans can be used. However, when it is desired to increase the concentration of the polymer, it is recommended to use a kneader type kneader as the dissolving can. By using a kneader type kneader, it is possible to stir even when the viscosity of the solution becomes high, and it is possible to shorten the time required for dissolution.
ケン化反応は、ビニルエステル系重合体のアルコール系溶液中にアルカリ触媒又は酸触媒を加えることで行う。アルカリ触媒としては、水酸化ナトリウム、水酸化カリウム、ナトリウムメチラート、ナトリウムエチラート、カリウムメチラート等のアルカリ金属の水酸化物やアルコラートの如きアルカリ触媒を用いることができる。また、アルカリ触媒の替わりに酸触媒を使用してもケン化することが可能である。酸触媒としては、塩酸、硫酸等の無機酸水溶液、p-トルエンスルホン酸等の有機酸を用いることができる。これらアルカリ触媒又は酸触媒の使用量はビニルエステル系単量体に対して1~100ミリモル当量にすることが必要である。
ケン化反応温度には、特に制限はないが、通常10~70℃の範囲であり、好ましくは30~50℃の範囲から選ぶのが望ましい。反応は通常15~180分間に渡って行われる。The saponification reaction is performed by adding an alkali catalyst or an acid catalyst to an alcoholic solution of the vinyl ester polymer. As the alkali catalyst, alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, sodium methylate, sodium ethylate and potassium methylate, and alkali catalysts such as alcoholates can be used. Saponification can also be carried out by using an acid catalyst instead of an alkali catalyst. As the acid catalyst, an inorganic acid aqueous solution such as hydrochloric acid or sulfuric acid, or an organic acid such as p-toluenesulfonic acid can be used. The amount of these alkali catalysts or acid catalysts to be used must be 1 to 100 millimol equivalents relative to the vinyl ester monomer.
Although the saponification reaction temperature is not particularly limited, it is usually in the range of 10 to 70°C, preferably in the range of 30 to 50°C. The reaction is usually carried out over 15-180 minutes.
ケン化に使用する反応装置は、特に限定されるものではなく、単軸スクリュー型、横二軸型、回転板型、縦二軸多段撹拌翼型、ベルト型、パイプ型、スラリー型等の連続方式、ニーダー型混練機等を利用したバッチ方式などの定法(非特許文献1参照)が使用可能である。
溶解工程でニーダー型混練機を使用した場合、引き続きニーダー型混練機中でケン化反応まで実施することが簡便である(非特許文献1)。The reaction apparatus used for saponification is not particularly limited, and may be a single-screw type, horizontal twin-screw type, rotating plate type, vertical twin-screw multi-stage stirring blade type, belt type, pipe type, slurry type, etc. A standard method such as a batch method using a kneader type kneader or the like (see Non-Patent Document 1) can be used.
When a kneader-type kneader is used in the dissolution step, it is convenient to carry out the subsequent saponification reaction in the kneader-type kneader (Non-Patent Document 1).
本発明の高重合度ポリビニルアルコールのケン化度は、特に制限されるものではなく、目的に応じて選定される。例えば、水溶性フィルムや接着剤向けに製造される場合はケン化度65~95モル%に、偏光膜原料用フィルムやガラス繊維から製造される不織布用のバインダー向けに製造される場合はケン化度98.0モル%以上に設定可能である。ケン化度は、JIS K6726:1994に準拠して測定される。すなわち、水酸化ナトリウムで試料中の残存酢酸基(モル%)を定量し、100から差し引くことで求めることができる。 The degree of saponification of the polyvinyl alcohol having a high degree of polymerization of the present invention is not particularly limited and is selected according to the purpose. For example, when manufactured for water-soluble films and adhesives, the degree of saponification is 65 to 95 mol%. The degree can be set to 98.0 mol % or more. The degree of saponification is measured according to JIS K6726:1994. That is, it can be obtained by quantifying the remaining acetic acid group (mol%) in the sample with sodium hydroxide and subtracting it from 100.
本発明で製造されるポリビニルアルコールは、生産性に優れ、また機械的強度に優れており、ビニロン繊維、水溶性フィルム、偏光膜用原料フィルム、紙用サイジング剤、繊維用サイジング剤、接着剤、懸濁重合用分散剤、乳化重合用分散剤、ポリブチラール樹脂用の原料などの様々な用途で使用可能である。 The polyvinyl alcohol produced by the present invention has excellent productivity and excellent mechanical strength, and can be used for vinylon fibers, water-soluble films, raw films for polarizing films, sizing agents for paper, sizing agents for fibers, adhesives, It can be used in various applications such as a dispersant for suspension polymerization, a dispersant for emulsion polymerization, and a raw material for polybutyral resin.
以下に、本発明を実施例に基づいて具体的に説明するが、本発明はこれに限定されるものではない。尚、特に断りがない限り、「部」及び、「%」はそれぞれ「質量部」及び「質量%」を意味する。なお、「実施例1」及び「実施例2」はそれぞれ参考例である。 EXAMPLES The present invention will be specifically described below based on Examples, but the present invention is not limited to these. Unless otherwise specified, "parts" and "%" mean "mass parts" and "mass%" respectively. In addition, "Example 1" and "Example 2" are reference examples, respectively.
また、実施例により得られた酢酸ビニル樹脂、及びポリビニルアルコールの物性測定は、下記に記載した方法によって実施した。 The physical properties of vinyl acetate resins and polyvinyl alcohol obtained in Examples were measured by the methods described below.
<酢酸ビニル樹脂のメジアン径>
メジアン径(d50)は、得られた酢酸ビニル樹脂を、レーザー回折式粒度分布装置[島津製作所製 SALD-3000S]を用い、測定用セルに蒸留水を加えて測定した。<Median diameter of vinyl acetate resin>
The median diameter (d50) of the obtained vinyl acetate resin was measured by adding distilled water to the measuring cell using a laser diffraction particle size distribution device [SALD-3000S manufactured by Shimadzu Corporation].
<酢酸ビニル樹脂の粒度分布(CV値)>
粒子径の分布は、レーザー回折式粒子径測定装置SALD-3000S(株式会社島津製作所製)を用いて、体積基準におけるメジアン径(d50)と、d50を基準としたときの標準偏差(σ50)を測定し、CV値(σ50/d50×100)を算出した。CV値は値が小さいほど粒子径の分布が狭いことを示す。<Particle size distribution (CV value) of vinyl acetate resin>
The distribution of the particle size was measured using a laser diffraction particle size measuring device SALD-3000S (manufactured by Shimadzu Corporation), and the median diameter (d50) on a volume basis and the standard deviation (σ50) based on d50 were measured. It was measured and the CV value (σ50/d50×100) was calculated. A smaller CV value indicates a narrower particle size distribution.
<溶解性の評価>
ビニルエステル系重合体のアルコール系溶媒に対する溶解性の評価は、未溶解物量が1000質量ppm以下を〇、1000質量ppm超を×として評価した。未溶解物量の測定は次の手順で行った。酢酸ビニル樹脂30gにメタノール800mLを加え、アンカー翼の撹拌機で回転数300rpmで3時間溶解を行った。その後、その溶液を150mesh(株式会社ハギテック製、ナイロン66PAスクリーン、150メッシュ、製品番号N-150T、目開き108μm、線径61μm)の濾布を用いてろ過し、濾布上に残った固形物の質量から未溶解物量を求めた。<Evaluation of solubility>
Evaluation of the solubility of the vinyl ester polymer in the alcohol solvent was evaluated as ◯ when the amount of undissolved matter was 1000 mass ppm or less, and x when it exceeded 1000 mass ppm. The amount of undissolved matter was measured by the following procedure. 800 mL of methanol was added to 30 g of vinyl acetate resin, and the mixture was dissolved with an anchor blade stirrer at a rotation speed of 300 rpm for 3 hours. Thereafter, the solution was filtered using a filter cloth of 150 mesh (manufactured by Hagitec Co., Ltd., nylon 66PA screen, 150 mesh, product number N-150T, mesh opening 108 μm, wire diameter 61 μm), and the solid matter remaining on the filter cloth The amount of undissolved matter was determined from the mass of
<付着性の評価>
付着性の評価は、ビニルエステル系重合体の反応停止後、未反応のビニルエステル系単量体を除去した後に、重合缶内にアルコール系溶媒に不溶の付着物が存在するかどうかを目視で評価した。重合缶内にそのような付着物が存在しない場合を〇、存在する場合を×として評価した。<Evaluation of adhesion>
Adhesiveness evaluation was carried out by visually checking whether there were any deposits insoluble in the alcoholic solvent in the polymerization vessel after the reaction of the vinyl ester polymer had stopped and after removing the unreacted vinyl ester monomer. evaluated. The case where such deposits were not present in the polymerization vessel was evaluated as ◯, and the case where such deposits were present was evaluated as x.
<酢酸ビニル樹脂の平均重合度(PAc)>
平均重合度は、JIS K6725-1977「ポリ酢酸ビニルの試験方法」の「3.2平均重合度」に準じて測定した。<Average Degree of Polymerization (PAc) of Vinyl Acetate Resin>
The average degree of polymerization was measured according to JIS K6725-1977 "Testing methods for polyvinyl acetate", "3.2 Average degree of polymerization".
<ポリビニルアルコールの平均重合度(PA)>
平均重合度は、JIS K6726:1994に準拠する方法にて測定した。すなわち、ポリビニルアルコールを完全にケン化し、精製した後、30℃の水中で測定した極限粘度[η]から求めた。<Average degree of polymerization of polyvinyl alcohol (PA)>
The average degree of polymerization was measured by a method according to JIS K6726:1994. That is, it was obtained from the intrinsic viscosity [η] measured in water at 30°C after completely saponifying and purifying polyvinyl alcohol.
<引張強度>
ポリビニルアルコールを純水に溶かし、加圧濾過装置(アドバンテック社製KST-90-UH)により異物を除去後、アプリケーターを用いて、上記ポリビニルアルコール水溶液をポリエチレンテレフタラートフィルム上にキャストして、乾燥させ、その後ポリエチレンテレフタラートフィルムから剥がすことによって膜厚15.0±1.0μmのフィルムを得た。ポリビニルアルコールフィルムを、20℃、60%RHで2日間室調後、引張試験を実施した。引張試験は、AG-X(島津製作所社製)を用いて、フィルムサンプル幅9.0mm、つかみ器具距離90.0mm、引張り速度50mm/分で行った。<Tensile strength>
Polyvinyl alcohol is dissolved in pure water, foreign matter is removed by a pressure filtration device (KST-90-UH manufactured by Advantech), and then the polyvinyl alcohol aqueous solution is cast on a polyethylene terephthalate film using an applicator and dried. and then peeled off from the polyethylene terephthalate film to obtain a film having a thickness of 15.0±1.0 μm. After conditioning the polyvinyl alcohol film at 20° C. and 60% RH for 2 days, a tensile test was performed. The tensile test was performed using AG-X (manufactured by Shimadzu Corporation) at a film sample width of 9.0 mm, a gripper distance of 90.0 mm, and a pulling speed of 50 mm/min.
(実施例1:懸濁重合)
還流冷却器、滴下漏斗、撹拌機を備えた重合缶に、酢酸ビニルモノマーを100質量部、水120質量部加え、窒素を1時間吹込み脱酸素を行った。その後開始剤であるV-70(アゾビス(4-メトキシ-2,4-ジメチルバレロニトリル))を0.018質量部及び、マレイン酸ジメチル変性PVAを分散剤として0.1質量部仕込み、15℃で重合し、酢酸ビニル樹脂の重合率が約30%に到達したところで重合停止剤であるt-ブチルカテコールを開始剤に対して2.0倍モル加えて反応を停止した(反応停止したときの重合率=30%)。
重合反応終了後、その容器を密閉し、内部を減圧状態に保ちながら、撹拌下70℃で、3時間未反応モノマーの除去を行った。得られた酢酸ビニル樹脂スラリーを冷却、濾過、水洗、脱水、乾燥等の処理を行って細粒状の平均重合度が18500の酢酸ビニル樹脂を得た。(Example 1: Suspension polymerization)
100 parts by mass of vinyl acetate monomer and 120 parts by mass of water were added to a polymerization vessel equipped with a reflux condenser, a dropping funnel and a stirrer, and nitrogen was blown in for 1 hour to remove oxygen. After that, 0.018 parts by mass of V-70 (azobis(4-methoxy-2,4-dimethylvaleronitrile)) as an initiator and 0.1 part by mass of dimethyl maleate-modified PVA as a dispersant were charged at 15°C. When the polymerization rate of the vinyl acetate resin reached about 30%, t-butyl catechol as a polymerization terminator was added in 2.0 times the molar amount of the initiator to terminate the reaction ( Polymerization rate = 30%).
After completion of the polymerization reaction, the vessel was sealed, and the unreacted monomers were removed at 70° C. for 3 hours while stirring while the inside was kept under reduced pressure. The resulting vinyl acetate resin slurry was subjected to treatments such as cooling, filtering, washing with water, dehydration and drying to obtain a vinyl acetate resin having an average degree of polymerization of 18500 in the form of fine particles.
ニーダー型混練機(容量:10リットル)にメタノール2200gを投入し、そこへ上記で得られた酢酸ビニル樹脂500g(不揮発分濃度=81.5%)を少量ずつ加えた。180分間撹拌を継続し、酢酸ビニル樹脂を完全に溶解した。
そこに10%の水酸化ナトリウムのメタノール溶液を添加し(酢酸ビニル100質量部に対し水酸化ナトリウム0.03質量部換算)、30℃で160分ケン化反応を行った。酢酸で中和後に、得られた固形分を加熱乾燥して、ケン化度99.4モル%、平均重合度が11800のポリビニルアルコールを得た。2200 g of methanol was charged into a kneader type kneader (capacity: 10 liters), and 500 g of the vinyl acetate resin obtained above (non-volatile content = 81.5%) was added little by little. Stirring was continued for 180 minutes to completely dissolve the vinyl acetate resin.
A methanol solution of 10% sodium hydroxide was added thereto (converted to 0.03 parts by mass of sodium hydroxide per 100 parts by mass of vinyl acetate), and a saponification reaction was carried out at 30° C. for 160 minutes. After neutralization with acetic acid, the obtained solid content was dried by heating to obtain polyvinyl alcohol having a degree of saponification of 99.4 mol % and an average degree of polymerization of 11,800.
上記で得られたポリビニルアルコールに対して、先述した方法でフィルムを作製し、引張試験を行って引張強度を求めたところ、フィルムの引張強度は72.2N/mm2であった。
これらの結果をまとめて表1に示した。A film was produced from the polyvinyl alcohol obtained above by the method described above and subjected to a tensile test to determine the tensile strength. The tensile strength of the film was 72.2 N/mm 2 .
These results are summarized in Table 1.
(実施例2~8:懸濁重合)
重合温度と重合率を表1のように変更した以外は、実施例1と同様に重合、ケン化を行い、その後、得られたポリビニルアルコールのフィルムを作製した。実施例1と同様の物性評価を行った結果を表1に示す。(Examples 2 to 8: Suspension polymerization)
Polymerization and saponification were carried out in the same manner as in Example 1 except that the polymerization temperature and polymerization rate were changed as shown in Table 1, and then the resulting polyvinyl alcohol film was produced. Table 1 shows the results of evaluation of physical properties in the same manner as in Example 1.
(比較例1~5:懸濁重合)
重合温度と重合率を表1のように変更した以外は、実施例1と同様に重合、ケン化を行い、その後、得られたポリビニルアルコールのフィルムを作製した。実施例1と同様の物性評価を行った結果を表1に示す。(Comparative Examples 1 to 5: Suspension polymerization)
Polymerization and saponification were carried out in the same manner as in Example 1 except that the polymerization temperature and polymerization rate were changed as shown in Table 1, and then the resulting polyvinyl alcohol film was produced. Table 1 shows the results of evaluation of physical properties in the same manner as in Example 1.
(比較例6:溶液重合)
還流冷却器、滴下漏斗、撹拌機を備えた重合缶に、酢酸ビニルモノマーを100質量部、メタノール14.3質量部、及び重合開始剤としてアゾビスイソブチロニトリルを酢酸ビニルに対して20質量ppm仕込み、窒素気流下で撹拌しながら外温65℃で8時間重合を行った。重合率が56%に達した時点で重合反応溶液中にメタノール蒸気を吹き込んで未反応モノマーを除去した後、メタノールにて希釈して酢酸ビニル樹脂のメタノール溶液を調製し、平均重合度が3300の酢酸ビニル樹脂のメタノール溶液を得た。(Comparative Example 6: solution polymerization)
100 parts by mass of vinyl acetate monomer, 14.3 parts by mass of methanol, and 20 parts by mass of azobisisobutyronitrile as a polymerization initiator with respect to vinyl acetate were placed in a polymerization vessel equipped with a reflux condenser, a dropping funnel, and a stirrer. Polymerization was carried out at an external temperature of 65° C. for 8 hours while stirring under a nitrogen stream. When the polymerization rate reached 56%, methanol vapor was blown into the polymerization reaction solution to remove unreacted monomers, and the solution was diluted with methanol to prepare a methanol solution of vinyl acetate resin. A methanol solution of vinyl acetate resin was obtained.
上記で得られた酢酸ビニル樹脂のメタノール溶液に、水酸化ナトリウムのメタノール溶液を添加し、40℃で45分間ケン化反応を行った。得られたケン化反応溶液を加熱乾燥してケン化度99.1mol%、平均重合度が2450のポリビニルアルコール(PVA)を得た。 A methanol solution of sodium hydroxide was added to the methanol solution of the vinyl acetate resin obtained above, and a saponification reaction was performed at 40° C. for 45 minutes. The resulting saponification reaction solution was dried by heating to obtain polyvinyl alcohol (PVA) having a degree of saponification of 99.1 mol % and an average degree of polymerization of 2,450.
上記で得られたPVAのフィルムを実施例1と同様の手順で作製し、実施例1と同様の物性評価を行った結果を表1に示す。 The PVA film obtained above was produced in the same procedure as in Example 1, and the physical properties were evaluated in the same manner as in Example 1. The results are shown in Table 1.
(比較例7:溶液重合)
還流冷却器、滴下漏斗、撹拌機を備えた重合缶に、酢酸ビニルモノマーを100質量部、メタノール8.2質量部、及び重合開始剤としてアゾビスイソブチロニトリルを酢酸ビニルに対して12質量ppm仕込み、窒素気流下で撹拌しながら外温65℃で8時間重合を行った。重合率が40%に達した時点で重合反応溶液中にメタノール蒸気を吹き込んで未反応モノマーを除去した後、メタノールにて希釈して酢酸ビニル樹脂のメタノール溶液を調製し、平均重合度が4150の酢酸ビニル樹脂のメタノール溶液を得た。(Comparative Example 7: Solution polymerization)
100 parts by mass of vinyl acetate monomer, 8.2 parts by mass of methanol, and 12 parts by mass of azobisisobutyronitrile as a polymerization initiator per vinyl acetate were placed in a polymerization vessel equipped with a reflux condenser, a dropping funnel, and a stirrer. Polymerization was carried out at an external temperature of 65° C. for 8 hours while stirring under a nitrogen stream. When the polymerization rate reached 40%, methanol vapor was blown into the polymerization reaction solution to remove unreacted monomers, and then diluted with methanol to prepare a methanol solution of a vinyl acetate resin. A methanol solution of vinyl acetate resin was obtained.
上記で得られた酢酸ビニル樹脂のメタノール溶液に、水酸化ナトリウムのメタノール溶液を添加し、40℃で45分間ケン化反応を行った。得られたケン化反応溶液を加熱乾燥してケン化度99mol%、平均重合度が3050のPVAを得た。 A methanol solution of sodium hydroxide was added to the methanol solution of the vinyl acetate resin obtained above, and a saponification reaction was performed at 40° C. for 45 minutes. The resulting saponification reaction solution was dried by heating to obtain PVA having a degree of saponification of 99 mol % and an average degree of polymerization of 3,050.
上記で得られたPVAのフィルムを実施例1と同様の手順で作製し、実施例1と同様の物性評価を行った結果を表1に示す。 The PVA film obtained above was produced in the same procedure as in Example 1, and the physical properties were evaluated in the same manner as in Example 1. The results are shown in Table 1.
(重合停止剤の評価)
重合停止剤の評価は、重合中に重合停止剤を重合系内に添加し、その後、16時間20℃で冷却を行い、重合停止剤添加前の酢酸ビニルの重合率P1と重合停止剤添加後の酢酸ビニルの重合率P2を比較することにより評価した。重合停止剤の添加時から16時間20℃で冷却後の酢酸ビニルの重合率の増加(P2-P1)が5%以内である重合停止剤を○、5%超であるものを×として評価した。(Evaluation of polymerization terminator)
Evaluation of the polymerization terminator was carried out by adding the polymerization terminator to the polymerization system during polymerization, then cooling at 20° C. for 16 hours, and determining the polymerization rate P 1 of vinyl acetate before the addition of the polymerization terminator and the addition of the polymerization terminator. Evaluation was made by comparing the subsequent polymerization rate P2 of vinyl acetate. A polymerization terminator that increases the polymerization rate of vinyl acetate (P 2 −P 1 ) after cooling at 20° C. for 16 hours from the time of addition of the polymerization terminator is within 5%. evaluated.
(実験例A:懸濁重合)
還流冷却器、滴下漏斗、撹拌機を備えた重合缶に、酢酸ビニルモノマーを100質量部、水120質量部を加え、窒素を1時間吹込み脱酸素を行った。その後開始剤であるV-70を0.018質量部及び、マレイン酸ジメチル変性PVAを分散剤として0.1質量部仕込み、30℃で重合し、酢酸ビニル樹脂の重合率が27%に到達したところで重合停止剤であるt-ブチルカテコール(TBC)を表2に記載の質量部数加えて反応を停止した。その後20℃に冷却し、16時間静置後に重合率を測定すると28%であった。重合停止剤の評価を表2に記載した。(Experimental Example A: Suspension polymerization)
100 parts by mass of vinyl acetate monomer and 120 parts by mass of water were added to a polymerization vessel equipped with a reflux condenser, a dropping funnel and a stirrer, and nitrogen was blown in for 1 hour to remove oxygen. After that, 0.018 part by mass of V-70 as an initiator and 0.1 part by mass of dimethyl maleate-modified PVA as a dispersant were charged and polymerized at 30° C., and the polymerization rate of the vinyl acetate resin reached 27%. By the way, the polymerization terminator, t-butylcatechol (TBC), was added in the mass parts listed in Table 2 to stop the reaction. After that, it was cooled to 20° C., and after standing still for 16 hours, the polymerization rate was measured to be 28%. Evaluation of the polymerization terminator is described in Table 2.
(実験例B~C)
重合温度、重合率、並びに重合停止剤の種類及び添加量を表2のように変更した以外は、実験例Aと同様に重合を行い、重合停止剤の評価を行った。(Experimental examples B to C)
Polymerization was carried out in the same manner as in Experimental Example A except that the polymerization temperature, polymerization rate, and type and amount of polymerization terminator were changed as shown in Table 2, and the polymerization terminator was evaluated.
(実験例D)
還流冷却器、滴下漏斗、撹拌機を備えた重合缶に、酢酸ビニルモノマーを100質量部、水120質量部加え、窒素を1時間吹込み脱酸素を行った。その後、開始剤であるV-70を0.018質量部及び、マレイン酸ジメチル変性PVAを分散剤として0.1質量部仕込み、30℃で重合し、酢酸ビニル樹脂の重合率が38%に到達したところで空気(60mL/分)を30分間加えて反応を停止した。ここで、重合系内の気相中の酸素濃度が9%を超えないよう酸素の流量の調整を行った。その後20℃に冷却し、16時間静置後に重合率を測定すると40%であった。(Experimental example D)
100 parts by mass of vinyl acetate monomer and 120 parts by mass of water were added to a polymerization vessel equipped with a reflux condenser, a dropping funnel and a stirrer, and nitrogen was blown in for 1 hour to remove oxygen. After that, 0.018 parts by mass of V-70 as an initiator and 0.1 parts by mass of dimethyl maleate-modified PVA as a dispersant were charged and polymerized at 30°C until the polymerization rate of the vinyl acetate resin reached 38%. At this point, air (60 mL/min) was added for 30 minutes to stop the reaction. Here, the oxygen flow rate was adjusted so that the oxygen concentration in the gas phase in the polymerization system did not exceed 9%. After that, it was cooled to 20° C., and after standing for 16 hours, the conversion was measured to be 40%.
(実験例E、F:比較)
重合温度、重合率、並びに重合停止剤の種類及び添加量を表2のように変更した以外は、実験例Aと同様に重合を行い、重合停止剤の評価を行った。(Experimental Examples E and F: Comparison)
Polymerization was carried out in the same manner as in Experimental Example A except that the polymerization temperature, polymerization rate, and type and amount of polymerization terminator were changed as shown in Table 2, and the polymerization terminator was evaluated.
(ケン化条件がポリビニルアルコールの粒度に与える影響の検討)
(実施例α)
ニーダー型混練機(容量:10リットル)に、不揮発分が89.0%となるように酢酸ビニル樹脂(平均重合度:16000)とメタノールを加え、180分間撹拌を継続し、酢酸ビニル樹脂を完全に溶解した。
そこに10%の水酸化ナトリウムのメタノール溶液を添加し(酢酸ビニル100質量部に対し水酸化ナトリウム0.03質量部換算)、30℃で160分ケン化反応を行った。酢酸で中和後に、得られた固形分を加熱乾燥して、ケン化度99モル%、平均重合度が10200のポリビニルアルコールを得た。(Examination of the influence of saponification conditions on the particle size of polyvinyl alcohol)
(Example α)
Vinyl acetate resin (average degree of polymerization: 16000) and methanol were added to a kneader type kneader (capacity: 10 liters) so that the non-volatile content was 89.0%, and stirring was continued for 180 minutes to completely dissolve the vinyl acetate resin. dissolved in
A methanol solution of 10% sodium hydroxide was added thereto (converted to 0.03 parts by mass of sodium hydroxide per 100 parts by mass of vinyl acetate), and a saponification reaction was carried out at 30° C. for 160 minutes. After neutralization with acetic acid, the obtained solid content was dried by heating to obtain polyvinyl alcohol having a degree of saponification of 99 mol % and an average degree of polymerization of 10,200.
得られたポリビニルアルコールをJIS Z-8801-1(2006)の試験用ふるい-第一部:金属製網ふるいの規格に準じた目開き1.7mmの金属製の篩にかけたところ、篩上の量は26.0質量%であった。 The obtained polyvinyl alcohol was passed through a metal sieve with an opening of 1.7 mm according to the JIS Z-8801-1 (2006) test sieve-Part 1: metal mesh sieve standard. The amount was 26.0% by weight.
(実施例β~δ)
用いた酢酸ビニル樹脂の平均重合度とメタノールに対する濃度(不揮発分)を表3のように変更した以外は、実施例αと同様にケン化を行い、得られたポリビニルアルコールの粒度の評価を実施例αと同じ篩を用いて篩上に残った質量割合を評価することで行った。(Examples β to δ)
Saponification was performed in the same manner as in Example α, except that the average degree of polymerization of the vinyl acetate resin used and the concentration (non-volatile content) relative to methanol were changed as shown in Table 3, and the particle size of the resulting polyvinyl alcohol was evaluated. The same sieve as in Example α was used to evaluate the mass fraction remaining on the sieve.
(比較例ε)
ニーダー型混練機(容量:10リットル)に、不揮発分が91.6%となるように酢酸ビニル樹脂(平均重合度:16000)とメタノールを加え、180分間撹拌を継続し、酢酸ビニル樹脂を完全に溶解した。
そこに10%の水酸化ナトリウムのメタノール溶液を添加し(酢酸ビニル100質量部に対し水酸化ナトリウム0.03質量部換算)、30℃で160分ケン化反応を行った。酢酸で中和後に、得られた固形分を加熱乾燥して、ケン化度99モル%、平均重合度が10200のポリビニルアルコールを得た。得られたポリビニルアルコールを実施例αと同じ篩にかけたところ、篩上の量は92.0質量%であった。(Comparative example ε)
Vinyl acetate resin (average degree of polymerization: 16000) and methanol were added to a kneader type kneader (capacity: 10 liters) so that the non-volatile content was 91.6%, and stirring was continued for 180 minutes to completely dissolve the vinyl acetate resin. dissolved in
A methanol solution of 10% sodium hydroxide was added thereto (converted to 0.03 parts by mass of sodium hydroxide per 100 parts by mass of vinyl acetate), and a saponification reaction was carried out at 30° C. for 160 minutes. After neutralization with acetic acid, the obtained solid content was dried by heating to obtain polyvinyl alcohol having a degree of saponification of 99 mol % and an average degree of polymerization of 10,200. When the obtained polyvinyl alcohol was passed through the same sieve as in Example α, the amount on the sieve was 92.0% by mass.
(比較例ζ)
不揮発分濃度を表3のように変更した以外は、比較例εと同様にケン化を行い、得られたポリビニルアルコールの粒度の評価を実施例αと同じ篩を用いて篩上に残った質量割合を評価することで行った。(Comparative example ζ)
Saponification was performed in the same manner as in Comparative Example ε except that the non-volatile content concentration was changed as shown in Table 3, and the particle size of the obtained polyvinyl alcohol was evaluated using the same sieve as in Example α. It was done by evaluating the ratio.
Claims (11)
ビニルエステル系重合体をアルコール系溶媒に溶解する工程と、
溶解されたビニルエステル系重合体のアルコール系溶液にケン化触媒を加えてケン化反応を行う工程と、
を含む、JIS K6726:1994で規定される平均重合度が5.0×103以上1.5×104以下であるポリビニルアルコールの製造方法。 a step of suspension polymerization of a vinyl ester monomer at a polymerization temperature of 25 ° C. or higher and 50° C. or lower at a polymerization rate of 10% or higher and 70% or lower to obtain a vinyl ester polymer;
a step of dissolving a vinyl ester-based polymer in an alcohol-based solvent;
a step of adding a saponification catalyst to the alcohol-based solution of the dissolved vinyl ester-based polymer to perform a saponification reaction;
A method for producing polyvinyl alcohol having an average degree of polymerization of 5.0×10 3 or more and 1.5×10 4 or less as defined in JIS K6726:1994 .
X ≦ -0.05T2+1.5T+60 式(1)
(式(1)において、Tは重合温度(℃)を表し、Xは重合率(質量%)(0<X<100)を表す。) 2. The method for producing polyvinyl alcohol according to claim 1, wherein the polymerization temperature (T) of the suspension polymerization and the polymerization rate (X) of the vinyl ester monomer are set so as to satisfy the following formula (1).
X≦−0.05T 2 +1.5T+60 Formula (1)
(In formula (1), T represents polymerization temperature (° C.), and X represents polymerization rate (% by mass) (0<X<100).)
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